We are studying the regulation of tubulin synthesis in the developing chick embryo brain. We propose to clone tubulin complementary DNA in the plasmid pBR322. The cloned DNA will be used as a probe to estimate the number of tubulin genes from a Southern blot of restricted total chick DNA fragments. We are also studying the pattern of tubulin subunit synthesis in the developing brain by quantitative two-dimensional gel electrophoresis.